LiMnO2 is obtained from NaMnO2 via Li-->Na exchange in molten LiI. The material crystallizes in an ordered rocksalt structure of idealized cationic distribution {Li2}16c [Mn2]16dO4 (space group Fd3m). A second new method for the preparation of isotypic LiMnO2 consists of Li intercalation via molten LiI into the spinel Li[Mn2]O4.LiFeO2, with a layered ordered rocksalt structure of alpha-NaFeO2 type (R3mBAR) is obtained from NaFeO2 via Li-->Na exchange in an eutectic melt of LiCl and LiNO3, whereas due to their higher melting points the employment of pure Li halides results in the formation of the alpha-LiFeO2 type (Fm3m) with disordered rocksalt structure.